Field of the Invention
The present invention relates to a liquid ejection head for ejecting liquid, such as ink, from an ejection port and a method for manufacturing the same.
Description of the Related Art
A recording system by a liquid ejection head typified by an inkjet recording head gives thermal energy or vibration energy to liquid, such as ink, to eject the ink in the form of small liquid droplets from an ejection port to form an image on a recording medium.
As methods for manufacturing the liquid ejection head of this type, the following method is mentioned. First, an ejection energy generating element and a wiring conductor for supplying electric power to the ejection energy generating element are provided on a silicon substrate. Then, a protective film is provided on the wiring conductor, and then an ink flow passage and an ink ejection port are patterned using a resist as a mask. Next, a through hole (ink supply port) for supplying ink is opened from the back surface side of the silicon substrate to the front surface side on which the ejection energy generating element is provided to form a substrate (recording element substrate).
Then, the formed recording element substrate is stuck to a concave portion containing a support member containing alumina or the like, and then a lead of an electric wiring member bonded onto the support member and an electrode terminal of a wiring conductor end of the recording element substrate are electrically bonded to each other.
Next, a chip periphery sealing material is applied to a gap between the support member and the recording element substrate on the periphery of the recording element substrate. An ILB (inner lead bonding) sealing material which seals the electric connection portion is applied from the above. As a technique relating to the chip periphery sealing, a method described in Japanese Patent Laid-Open No. 2005-132102 is known.
Functions required in the chip periphery sealing material used herein which seals the periphery of the recording element substrate are as follows.
First, as the first point, it is required that, when the head is manufactured, the periphery sealing material flows in a short time through the gap having a width of a little less than 1 mm formed between the concave portion on the support member and the recording element substrate, so that the periphery sealing material is promptly filled into the entire periphery from the injection point thereof.
As the second point, it is required that corrosion of the electric connection portion, short circuit, and migration due to ink and other factors are prevented as the quality of the head.
As the third point, it is required that the element substrate is not deformed due to expansion and shrinkage of the sealing material. In the head having the above-described configuration, it is common to use a single crystal silicon for the recording element substrate. Since the periphery sealing material seals the periphery of the element substrate, the periphery sealing material having a large linear expansion coefficient further shrinks as compared with the element substrate having a very small linear expansion coefficient in an environment where the temperature is lower than the curing temperature of the periphery sealing material. When the periphery sealing material shrinks, force (tensile stress) is applied in a direction in which the periphery sealing material outwardly pulls the element substrate. When the shrinkage of the periphery sealing material is large, cracking may occur in the element substrate due to the tensile stress, which may make it impossible to perform good printing.
In order to reduce such tensile stress, it is advantageous to reduce the linear expansion and reduce the elasticity of the chip periphery sealing material. Therefore, a method of filling a large amount of a filler into the chip periphery sealing material is mentioned. For example, since a silica filler is an inorganic substance, the linear expansion coefficient is small. Thus, by filling a larger amount of the silica filler into the periphery sealing material containing a base resin which is an organic substance, the linear expansion coefficient can be further reduced. A silicone filler is a low elastic filler. Therefore, by filling a larger amount of the silicone filler into the periphery sealing material, the elasticity can be further reduced. However, high filling of the filler leads to a reduction in fluidity of the filler. As described above, since the periphery sealing material needs to promptly flow through a gap having a width of a little less than 1 mm, both high fluidity and high filling of the filler need to be achieved.
The silica filler and the silicone filler are usually mixed into the base resin forming the sealing material under heating or cooling as necessary with a planetary mixer, a triple roll, or the like. However, the silicone filler is viscous powder. Therefore, when the silicone filler is mixed with the base resin as it is, the silicone filler cannot be uniformly dispersed in the base resin, which leads to the formation of a sealing material having high viscosity and high thixotropy. Thus, the silicone filler cannot be used for the chip periphery sealing material which is required to have high fluidity in some cases.
Therefore, in order to uniformly disperse the silicone filler in the chip periphery sealing material, it is known that the uniform dispersion of the silicone filler can be achieved by the use of a dispersant.
Japanese Patent Laid-Open Nos. 2008-214479 and 2014-152310 describe dispersing the silicone filler without increasing the viscosity and the thixotropy using a dispersant.
In Japanese Patent Laid-Open No. 2008-214479, a viscosity reduction is achieved by the use of silicone oil as the dispersant (which is indicated as a compatibilization agent in Japanese Patent Laid-Open No. 2008-214479). In Japanese Patent Laid-Open No. 2014-152310, the viscosity is reduced by the use of a silane coupling agent as the dispersant.